With the continuous development of liquid crystal technology, the requirement for the internal components of a liquid crystal display (LCD) is higher and higher.
Referring now to FIG. 1, a structural schematic view of a side-light type of backlight module in a traditional technology is illustrated in FIG. 1. In this figure, a light source 11 is disposed at one side of a light guide plate 12. The lights emitted from the light source 11 enter into the light guide plate 12, and then enter into an optical film 13.
Above-mentioned technology that the light guide plate 12 guides the lights of the light source 11 has problems as follows:
Firstly, because the light guide plate 12 has a characteristic of thermal expansion, the light source 11 and a light in surface of the light guide plate 12 can not achieve to seamless connection, so as to limit the improvement of the light coupling efficiency. Besides, the light source 11 has a certain size and the angular aperture of the light source 11 is larger, such as the angular aperture of an light emitting diode (LED) can approach to 90 degree, but the thickness of the light guide plate 12 is fixed, so that it is easy to cause a light leakage from the larger angle of the light source 11.
Secondly, the material of the light guide plate 12 can absorb one part of lights. For example, if the structure of the light guide plate 12 is adopted dot structures, the dot structures will absorb one part of lights, so it will lower the light utilization rate. Besides, the material of the light guide plate 12 has different absorbed rate to different wave frequency, so that with the increasing of the transmission distance in the light guide plate 12, a light out surface 122 of the light guide plate 12 will appear a chromatism phenomenon.
Thirdly, with a development trend of the LCD is toward light-thin and reduction, it is necessary to simplify the LCD structure, but the existence of the light guide plate 12 obstructs the light-thin development of the LCD. Besides, the light guide plate 12 will increase the complexity in design of the backlight module, such as considering of that a warp phenomenon will happen in the light guide plate 12, so that the designing accuracy of components inside the LCD needs to be readjusted. Therefore, the material cost of the light guide plate 12 is expensive, so that the manufacture cost of the LCD will be increased.
Because of that: the light coupling efficiency between the light guide plate 12 and the light source 11 is low; the lights absorbed by the light guide plate 12 lower the light utilization rate causing the chromatism phenomenon; and the light guide plate 12 obstructs the light-thin development trend of the LCD, so as to increase the design complexity and cost and so on. Hence, it is necessary to research a technology to omit the light guide plate 12.
However, the reflection rate on the optical film 13 is uniform, so in a backlight mode of side light in, with the distances with the light source 11 are different, each of parts of the optical film 13 get the different illumination intensity and luminous flux. If the light guide plate 12 is omitted, and in the condition of that the reflection rate on the optical film 13 is uniform, the lights emitted to the optical film 13 can not be uniform, so it will cause a chromatism phenomenon.
As described above, how to omit the light guide plate and to ensure the lights emitted to the optical film keeping uniform to avoid the chromatism phenomenon in such condition is become one of the research directions of the field of liquid crystal display technologies.